Waltz Mill facility tests underground cables and also demonstrates feasibility of 1100-kV overhead systems

The Waltz Mill facility serves for accelerated testing of sample insulation and other evaluations that require a continuous high voltage, circulating load current, and computerized temperature and process control. The area is divided into a highvoltage test area where controlled three-phase voltage up to 345 kV is available, and an extra-high-voltage test area where control three-phase voltage up to 1100 kV is available. Testing of four 550-kV underground cable systems was performed in the EHV area. The system will be subjected to higher voltages and temperatures to establish their capability with 800 kV as a prime objective. Computers were developed for the management of accelerated life testing of cable samples. The four general types are data collecting and processing, alarming and detection of abnormal conditions, reports, and control programs. Dielectric dissipation factor values verify the performance of paper-insulated cables and a transformer ratio-arm bridge is used for these measurements. Partial discharge measurements on soliddielectric cables are recorded with a differential corona bridge. The measuring procedures are described. (MCW)